Currently, drilling perpendicular, parallel or at any other specified angle manually is done by “eyeballing” the angle between the tool and the surface. Because visual judgment is imprecise, it is difficult to achieve the desired results with this method. Subsequently developed mechanical means, such as telescoping drill guides or bubble levels, have also proved to be insufficient.
Generally, mechanical means tend to be bulky and implement-specific, and therefore expensive and inconvenient. Specifically, U.S. Pat. No. 4,154,001 by Serafino is tool-specific and requires considerable set-up time. Similarly, telescoping guides interfere with normal functioning of the implement, because the guide rests on the surface to be drilled.
Consequently, the guide must be attached and detached from the tool depending on whether or not the particular use requires perpendicularity.
Bubble levels are impractical as well, because 1) they require the operator to concentrate on the level rather than surface to be drilled and 2) they must be customized to the angle of the drilling surface, especially if the surface is not horizontal (level) or vertical (plumb).
U.S. Pat. No. 4,125,944 by Esposito et al., shows one example of such device using a bubble level for tool alignment. However, if the surface to be drilled is not precisely horizontal or vertical, this tool is no longer usable. A similar device described in the U.S. Pat. No. 4,656,749 by Ashley et al., is also not usable on any fixed surface that is not perfectly horizontal or vertical.
U.S. Pat. No. 5,302,833 by Hamar et al. discloses a laser alignment control system for aligning a rotational portion of a machine tool to a master part. The system includes a laser emitter that is mountable to one of the components being aligned, a photosensitive target mountable to the other components, a data acquisition subsystem for receiving signals from the target and calculating alignment errors and required corrections for the system, and a rotational orientation sensor operatively connected to the data acquisition subsystem. The system is bulky, complex and the alignment procedure requires rotating the target for the laser emitter in the rotating tool holder or the master part. Similar drawbacks are present in an apparatus for obtaining mutual angular alignment of two remotely positioned objects disclosed in the U.S. Pat. No. 4,306,806 by Barron. This apparatus comprises a collimated light source associated with one of the two objects, a prism associated with the other of the two objects, and a viewing screen or device for viewing images created by the light source and the prism.
U.S. Pat. No. 5,596,403 by Schiff et al. discloses a system for measuring relative angular position of two objects, which includes a source assembly and a receiver assembly. A source assembly emits a rotationally polarized carrier wave laser beam. A laser beam from a laser diode is directed through a linear polarizer and then through the center of a rotating half-wave plate. The plate is secured to a hollow shaft of an electric motor. The beam travels through the plate and through the hollow shaft. A reference signal corresponding to the rotational modulation imposed by the rotating plate is obtained using a flag which is secured to the shaft and positioned to actuate an optical encoder. After leaving the source assembly and reaching the receiver assembly, the beam travels through another linear polarizer, a neutral density filter, and an aplanatic achromatic lens to a two-dimensional position sensing detector. The system is complex and unusable for hand held tools.
U.S. Pat. No. 6,692,200 by Peterson incorporated herein by reference discloses a system incorporating a laser beam, which reflects from a housed mirror to a translucent screen affixed to the housing. Alignment can be verified when the reflected laser beam is coincident with the emitted laser beam as seen on the translucent screen, thus indicating perpendicularity. This system is flawed in that the translucent screen is placed close to the mirror. The closer the translucent screen (detector) is to the mirror (reflector) the greater is the inaccuracy of the system. This system is further limited in that the operator of the device must be substantially at a visual vantage point that is perpendicular to the translucent screen in order to make use of this device. Additional relevant prior art is described in the German Patent No. DE10013943, Japanese Patent No. JP5309508, and PCT Application No. WO03041916, all incorporated herein in their entirety by reference. These patents describe various drill alignment devices based on a light beam reflected from the target surface and providing therefore a means for tool alignment.
The need exists, therefore, for an inexpensive, non-implement-specific, simple and easy-to-use device that can aid in visual alignment of handheld tools on any flat surface from an omni directional line-of-sight.